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Steam radiator issue

pqc Member Posts: 4
I have an old single pipe steam system. Some of the radiators do not completely heat...the top half of them are smoking...the lower half of them are barely warm. I have cleaned and changed the valves on them. Is it possible that there is water in the lower half?


  • Jamie Hall
    Jamie Hall Member Posts: 23,324
    Very unlikely. Like VERY unlikely. Where on the outlet side of the radiators are the vents set? They should be no more than half way up -- many times about a third of the way up -- from the bottom.

    Besides that, it is not at all uncommon for steam radiators to not be completely hot all over. The question isn't is the radiator hot all over, but is the radiator putting out enough heat to keep the space warm?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • pqc
    pqc Member Posts: 4
    Jamie Hall...thanks for the response! I pretty much knew that...but am baffled at the stark difference between the top and bottom temps and the fact that they're not all that way. Generally, yes, they handle the space and yes, the vents are placed properly on the radiator.
  • BobC
    BobC Member Posts: 5,478
    What model air vents are you using? Do the radiators have a top passage for the steam or are they steam only radiators with no steam connection at the top? If your venting very fast with a heatimer or Gorton c or d the steam can act a bit funny.
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846
    If the vents are closing before all the air gets voided, then the steam will rise to the top. We see this when the vents are too fast and the steam shoots across and hits the vent without pushing all the air ahead of it. Once the air gets trapped, it will settle to the bottom and stay there even though the top of the radiator continues to condense steam and give off heat. Try a slower vent.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • ChrisJ
    ChrisJ Member Posts: 15,706
    Are the rooms too cool?
    Is the boiler cycling a lot during a single call for heat?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment